Add benchmarks for json read

Author: NathanielRN

tests/mock_sampling_rule.json

@@ -0,0 +1,9 @@
+{
+    "version": 2,
+    "default": {
+      "fixed_target": 1,
+      "rate": 0.05
+    },
+    "rules": [
+    ]
+  }

tests/test_local_sampling_benchmark.py

@@ -0,0 +1,16 @@
+import json
+import pkgutil
+from pkg_resources import resource_filename
+
+from aws_xray_sdk.core.sampling.local.sampler import LocalSampler
+
+def test_pkg_resources_static_read(benchmark):
+    def get_sampling_rule():
+        with open(resource_filename(__name__, 'mock_sampling_rule.json')) as f:
+            return json.load(f)
+    benchmark(get_sampling_rule)
+
+def test_pkgutil_static_read(benchmark):
+    def get_sampling_rule():
+        json.loads(pkgutil.get_data(__name__, 'mock_sampling_rule.json'))
+    benchmark(get_sampling_rule)

tox.ini

@@ -16,6 +16,7 @@ skip_missing_interpreters = True
 passenv = TOXENV CI TRAVIS TRAVIS_* CODECOV_*
 deps =
     pytest > 3.0.0
+    pytest-benchmark
     coverage==4.5.4
     codecov
     requests